Squats on the Smith machine. This is a squat you do standing at a machine that has a barbell on a sliding track. The barbell rests on your shoulders, behind your head. On the machine, the bar doesn't give, so it forces the body into disadvantageous biomechanical positions," says exercise physiologist and fitness consultant, Joseph Warpeha. People also tend to put their feet further in front of their bodies when doing squats on the machine, which adds to the problem.

Any exercise done wearing the wrong shoes. Even if you're doing everything else right, your efforts can be undermined by improper footwear, warns Saremi, a podiatrist and editorial staff member of the Aerobic and Fitness Association of America's American Fitness magazine. Working out with the wrong shoes increases pounding on the joints, and can lead to injuries like plantar fasciitis or tendinitis, she says.

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Exercises done with the goal of spot reduction. People who do strengthening and toning exercises in an effort to trim fat from a certain area – thighs, hips, stomach, or arms – have the wrong idea. While these exercises can help firm muscles, if the targeted area still carries an extra layer of fat, it won't look much different.

Using bad form on cardio machines. Walk into any gym and you'll see some people sweating through their treadmill, elliptical, or stair-climber workouts with their bodies hunched over and a death grip on the handrails. Use a natural gait, says Scott Danberg, MS, director of sp and fitness for Pritikin Longevity Center and Spa in Aventura, Fla. And "Don't hold the handrails because it breaks the natural biomechanics of the body. We don't go through life holding on to something."

Always lifting with a weight belt. Bodybuilders have long used these belts to provide low back and abdominal support when lifting heavy weights. But now they seem to be standard equipment even for many occasional weightlifters. Unless you have a back injury or another medical reason to use the belt, says Warpeha, the level at which the average person works doesn't require a weight belt. And it can do more harm than good.

"Don't hold the handrails because it breaks the natural biomechanics of the body."
What the heck does that mean? What is so bad about holding onto the handrails? I always do it when I'm on an elliptical, because the handles are there and I have a little, erm, issue with balance.

I see way too many young girls hunched over the cardio machines, hanging on to the side bars for dear life while running at super-fast speeds. Many of them get so overworked that then rest by standing with their feet on the sides of the machine while the treadmill whirs along, when they should be walking at a slower pace for interval cardio training. There's this one particular girl that will jog at such a high speed that she props herself up on the side bars of the treadmill so her feet can skip along by barely touching the machine. How do these girls think these are proper workouts?

I do squats on the Smith machine and although I support them, I understand what you're saying. After months on the Smith machine, I switched to hack squats and saw immediate results. Now I warm up on the Smith machine but don't rely on it for muscle-building.

Doing squats with just a bar + weights versus a machine is advantageous because you have to use more of your muscles to keep your overall balance as you proceed through the squat. Doing a squat freely like that, with correct form and lowering yourself so your knees are nearly at 90 degrees, gets the most out of the motion. The Smith machine restricts your motion. When you do a squat "naturally" your shoulders aren't necessarily exactly under where there are when you're standing.Weight belts aren't necessary for the "light" lifter, but if you are straining under squats, or doing dead lifts, cleans, or jerks, I would say they are beneficial.

Doing squats with just a bar + weights versus a machine is advantageous because you have to use more of your muscles to keep your overall balance as you proceed through the squat. Doing a squat freely like that, with correct form and lowering yourself so your knees are nearly at 90 degrees, gets the most out of the motion. The Smith machine restricts your motion. When you do a squat "naturally" your shoulders aren't necessarily exactly under where there are when you're standing.
Weight belts aren't necessary for the "light" lifter, but if you are straining under squats, or doing dead lifts, cleans, or jerks, I would say they are beneficial.

I sometimes use bad form when I'm on my elliptical, I think. Usually, I don't hang onto the handles, but when the resistance is really high, I do. I used to do the Smith Machine squats, but I quit doing that because now I don't have access to one so I just use the regular barbells to do them. I guess they DO feel more natural than the machine now that I think about it.

The Smith machine explanation doesn't even make sense. How does the bar give if you're just using a regular barbell? I've been doing squats and lunges for years on the Smith machine and I've never had any problems.

Aaawww, I love smith machine squats! I like doing quick "pulses" of squats at the end of each set, and I like squatting down, then bringing one knee up at the top of the movement. I'm pretty sure my form is good...

I will sometimes hold on when walking fast on the treadmill, but its only when I'm up in the super high elevations, and it's so I don't slide off the back. I mean like elevations over 10. I do notice that my back and arms get a little sore, but I definitely concentrate that I am keeping up the speed and not holding on with a death grip.